Thanks to all for the many advices. I will go ahead and purchase a new set of sponge filter and do frequent water changes. My remaining frys are almost a month old and are close to being 3/4" . Should have asked this question long before. From the time my pair spawned, there was about 50 frys that hatch out of a possible 80 or so eggs, but despite the freqent water change I did, frys keep dying one by one and now down to 4 left but these 4 I think will hold up since they are large enough compared to the others that were a bit smaller. I have another pair that seems to be ready to spawn so I'll follow your advices and hope to raise a larger number of frys. Many thanks again, you guys and gals are great!